A synchronous reluctance type rotary electric machine includes a rotor and a stator. The rotor includes a shaft rotatably supported and extending in an axial direction at a center of the rotating shaft, and a rotor core externally fitted and fixed to the shaft. The stator includes a stator core disposed on an outer circumference of the rotor core to be spaced apart from the rotor core and having a plurality of teeth disposed at intervals in a circumferential direction, and multipole multiphase armature windings respectively wound around the plurality of teeth.
Multi-layered hollow parts having a convex shape toward the side radially inward are formed for each pole in the rotor core. When the hollow parts are formed in this manner, a direction in which magnetic flux easily flows and a direction in which magnetic flux does not easily flow are formed in the rotor core. Thus, the synchronous reluctance type rotary electric machine rotates the shaft using a reluctance torque generated by the hollow parts.
Incidentally, at the time of starting a synchronous reluctance type rotary electric machine, it is necessary to detect a relative position between the stator core and the rotor core and to supply electric power to predetermined armature windings on the basis of the relative position. Therefore, an inverter is required to start the synchronous reluctance type rotary electric machine, which may increase the costs of the synchronous reluctance type rotary electric machine.
Thus, in order to start the synchronous reluctance type rotary electric machine without using an inverter, a so-called self-starting type synchronous reluctance type rotary electric machine in which a nonmagnetic conductor is provided in the hollow parts to generate an induced torque has been proposed.
Here, in order to reduce leakage magnetic flux at an outer circumferential portion of the rotor core, the hollow parts are formed as close as possible to the outer circumferential surface of the rotor core. Therefore, for example, when an end portion on the outer circumferential surface side of the rotor core in the hollow part is filled with a conductor, since the magnetic flux pulsating according to a pitch of teeth of the stator links with the conductor, a harmonic current that does not contribute to rotation of the rotor flows through the conductor. Since this harmonic current is converted into Joule heat, there is a likelihood of the efficiency of the synchronous reluctance type rotary electric machine decreasing according to that amount.
Also, the magnetic flux flowing through the rotor core decreases in magnetic flux density toward a radial center of the rotor core. Therefore, for example, when the entire hollow part is filled with a conductor, there may be a portion that hardly contributes to the induced torque in the conductors. Therefore, the weight of the rotor core is unnecessarily increased, and thereby there is a likelihood of not only increasing manufacturing costs but also decreasing efficiency of the synchronous reluctance type rotary electric machine.